Surgical access devices and methods of minimally invasive surgery

ABSTRACT

A surgical access device includes a proximal frame of fixed construction and a plurality of tissue engaging blades connected to the frame. The plurality of tissue engaging blades may include a first blade that is rotatable, independent of other blades, about an axis that is oriented approximately parallel to a plane defined by the proximal frame.

BACKGROUND

In surgical procedures, it is important to minimize trauma to the patient and damage to tissue to facilitate patient recovery. One way to accomplish this is to minimize the size of the incision for the surgical procedure and minimize the cutting of tissue to access the target anatomy. A number of retractors are available that are designed to expand a small surgical incision and provide access to a surgical site. Such retractors typically include two or more retractor blades that separate to expand the incision and create an access channel through which to conduct the surgical procedure. One problem with such retractors is that the access channel of the expanded retractor is often restricted to one shape or configuration.

SUMMARY

Disclosed herein are surgical access devices and methods of minimally invasive surgery that minimize tissue trauma and facilitate access to a surgical site. In one exemplary embodiment, a surgical access device may comprise a proximal frame of fixed construction and a plurality of tissue engaging blades connected to the frame. The plurality of tissue engaging blades may include a first blade that is rotatable, independent of other blades, about an axis that is oriented approximately parallel to a plane defined by the proximal frame.

In accordance with another exemplary embodiment, a surgical access device may comprise a proximal frame of fixed construction, a first blade rotatably connected to the proximal frame and rotatable about a first axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame, a second blade rotatably connected to the proximal frame and rotatable about a second axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame, a third blade rotatably connected to the proximal frame and rotatable about a third axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame, and a fourth blade rotatably connected to the proximal frame and rotatable about a fourth axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame. In the exemplary embodiment, the second blade may be positioned opposite the first blade, the third blade may be positioned between the first blade and the second blade, and the fourth blade being positioned opposite the third blade.

In accordance with another exemplary embodiment, a method of providing minimally invasive access to spinal anatomy may comprise making an incision and inserting a plurality of blades of a surgical access device through the incision. The surgical access device may comprise a proximal frame of fixed construction and the plurality of blades may be connected to the proximal frame. The exemplary method may further include advancing the distal ends of the plurality blades into proximity to the spinal anatomy with the blades in a closed configuration in which the blades contact each other to form a continuous enclosed access channel between the frame and the distal ends of the blades. The exemplary method may also include rotating a first one of the blades independent of the other blades about a rotation axis that is oriented approximately parallel to an axis defined by the proximal frame to expand the access channel.

BRIEF DESCRIPTION OF THE FIGURES

These and other features and advantages of the devices and methods disclosed herein will be more fully understood by reference to the following detailed description in conjunction with the attached drawings in which like reference numerals refer to like elements through the different views. The drawings illustrate principles of the devices and methods disclosed herein and, although not to scale, show relative dimensions.

FIG. 1 is a perspective view of an exemplary embodiment of a surgical access device, illustrating the device in a closed configuration;

FIG. 2 is perspective view of the surgical access device of FIG. 1, illustrating the device in an expanded configuration;

FIG. 3 is an exploded view of the surgical access device of FIG. 1;

FIG. 4 is a side view in cross section of the surgical access device of FIG. 1, illustrating the device in a closed configuration;

FIG. 5 is a side view in cross section of the surgical access device of FIG. 1, illustrating the device in an expanded configuration;

FIG. 6 is a perspective view of another exemplary embodiment of a surgical access device, illustrating the device in a closed configuration;

FIG. 7 is perspective view of the surgical access device of FIG. 6, illustrating the device in an expanded configuration;

FIG. 8 is a top view of the surgical access device of FIG. 6;

FIGS. 9A and 9B are side views in cross section (along different section lines) of the surgical access device of FIG. 6, illustrating the device in an expanded configuration (FIG. 9A) and in a closed configuration (FIG. 9B);

FIG. 10 is a partial side view in cross section of another alternative embodiment of a surgical access device, illustrating an exemplary connection node of the surgical access device;

FIG. 11 is a partial side view in cross section of another alternative embodiment of a surgical access device, illustrating an exemplary connection node of the surgical access device

FIG. 12 is a partial side view in cross section of another alternative embodiment of a surgical access device, illustrating an exemplary connection node of the surgical access device; and

FIG. 13 is a partial side view in cross section of another alternative embodiment of a surgical access device, illustrating an exemplary connection node of the surgical access device.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

The articles “a” and “an” are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.

The terms “comprise,” “include,” and “have,” and the derivatives thereof, are used herein interchangeably as comprehensive, open-ended terms. For example, use of “comprising,” “including,” or “having” means that whatever element is comprised, had, or included, is not the only element encompassed by the subject of the clause that contains the verb.

FIGS. 1-5 illustrate an exemplary embodiment of a surgical access device 10 suitable for providing a selectively expandable access channel through which a surgical procedure may be performed on target anatomy. The exemplary surgical access device is particularly suited for minimally invasive spine surgery and, to this end, may be inserted through a relatively small incision to provide a selectively expandable access channel from the skin to the target spinal anatomy. As discussed in more detail below, the exemplary surgical access device 10 includes a plurality of tissue engaging blades 12, some or all of which may be independently rotated to allow the access channel of the surgical access device 10 to be selectively expanded into a variety of different shapes and sizes.

The surgical access device 10 may include a plurality of tissue engaging blades 12. Any number of blades 12 may be provided. In the exemplary, illustrated embodiment, the surgical access device 10 includes four tissue engaging blades: first blade 12 a, second blade 12 b, third blade 12 c, and fourth blade 12 d. The first blade 12 a is positioned opposite the second blade 12 b and is interposed between the third blade 12 c and the fourth blade 12 d. In the illustrated exemplary embodiment, each blade 12 is analogous in size and shape and may include a proximal end 18 that is configured to facilitate connection of the blade 12 to the surgical access device 10. The proximal end 18 of the blades 12 may include a slot 19 for receiving an instrument employed to rotate the blade 12. In alternative embodiments, a surgical access device may include a plurality differently configured blades.

The exemplary surgical access device 10 further includes a frame 14 located at the proximal end of the surgical access device 10. The frame 14, in the exemplary embodiment, is generally clover-shaped having a central opening 24 that provide access to an access channel 20 defined by the blades 12 of the surgical access device 10. The frame 14 may include a plurality of the connection nodes 26 to facilitate connection of the blades 12 to the frame 14. In the exemplary embodiment, the frame 14 includes connection nodes 26 a-d for connecting the blades 12 a-d, respectively, to the frame 14. The plurality of blades 12 a-d may be directly connected to the frame 14 through the connection nodes 26 a-d, as in the exemplary embodiment, or, in other embodiments, may be indirectly connected to the frame 14. In the exemplary embodiment, the frame 14 has a fixed construction e.g., the frame 14 is fixed in size and shape and, thus, does not expand in use. Rather, one or more of the blades 12 a-d may be movable to allow the access channel 20 defined by the blades 12 of the surgical access device 14 to be selectively expanded. The frame 14 may be unitary in construction or may constructed from multiple components. The frame 14 includes a generally planar bottom surface 16 for engaging the surface of the skin about an incision when the surgical access device 10 is in use.

One or more of the blades 12 may be rotatably connected to the frame 14 such that the blade may rotate relative to the frame 14 to expand the access channel 20. In the illustrated exemplary embodiment, first blade 12 a, second blade 12 b, third blade 12 c, and fourth blade 12 d may each be rotatably connected to a respective connection node 26 a-d of the frame 14 and each may be rotated relative to the frame 14 independent of the other blades. In particular, each blade 12 a-d may be connected to a respective connection node 26 a-d of the frame 14 by a shaft 30 a-d that defines a rotation axis about which the blade 12 rotates relative to the frame 14. At each node 26, a shaft 30 may be positioned across the node 26 through openings 32 in the frame 14 and the shaft 30 may pass through an opening 34 provided through the proximal end 18 of the respective blade 12. In the exemplary embodiment, each shaft 30 a-d defines a rotation axis for a respective blade 12 a-d and each rotation axis is oriented approximately parallel to the plane defined by the bottom surface 16 of the frame 14. Each shaft 30 a-d may be positioned in a common plane, as in the illustrated exemplary embodiment, or may be positioned in separate planes.

In use, each blade 12 may be rotated about a respective shaft 30 between a first, closed position in which the blade 12 is oriented approximately perpendicular the plane defined by the bottom surface 16 of the frame 14, as illustrated in FIGS. 1 and 4, and a second, fully expanded position in which a portion of the blade 12, for example, the distal end of the blade, is displaced a distance from a central axis 50 of the access channel 20, as illustrated in FIGS. 2 and 5. One or more of the blades 12 may be independently rotated to any position between the first, closed position and the second, fully expanded position to selectively expand the access channel 20. When each blade 12 a-d is in the first, closed position, adjacent blades 12 are proximate to each other along the lateral edges of the blades 12 to form a continuously approximately enclosed access channel 20. In the exemplary embodiment, when each blade 12 a-d is in the first, closed position, adjacent blades 12 contact each other along the lateral edges of the blades 12 to form a continuously fully enclosed access channel 20. The cross sectional size and shape of the access channel 20 in the closed configuration may vary depending on, for example, the number of blades provided, the surgical procedure being performed and the designed approach, e.g., anterior, lateral, or posterior. In the exemplary embodiment, the blades 12 a-d form a cylindrical access channel 20 having a circular cross section when the blades 12 a-d are in the first, closed position. The amount of rotational adjustment for the blades between the first, closed position and the second, fully expanded position may be varied. For example, in the exemplary embodiment, each blade 12 may rotate approximately 45° between the first, closed position and the second, fully expanded position.

The surgical access device 10 may include a blade adjustment mechanism for selectively adjusting the rotational position of a rotationally adjustable blade. In the illustrated exemplary embodiment, for example, the blade adjustment mechanism may be a pawl 60 pivotally connected to the frame 14 for selectively engaging a plurality of teeth 70 provided on the proximal end 18 of a blade 12. For example, each connection node 26 a-d of the exemplary surgical access device 10 may include a pawl 60 a-d pivotally connected thereto. In particular, referring to connection node 26 b for example, the connection node 26 b may include a shaft 62 b positioned through openings 64 b provided in the frame 14 and through an opening 66 b in the pawl 60 b. The pawl 60 b may pivot about the shaft 62 b into and out of engagement with the teeth 70 b provided on the proximal end 18 b of the second blade 12 b. The pawl 60 b may be biased into engagement with the teeth 70 b of the second blade 12 b by, for example, a spring 68 b. The teeth 70 b may be provided on an arcuate surface 72 b of the proximal end 18 b of the second blade 12 b to facilitate rotational positioning of the second blade 12 b. When the pawl 60 b is engaged with the teeth 70 b of the second blade 12 b, the pawl 60 b inhibits rotation of the second blade 12 b. When the pawl 60 b is pivoted out of engagement with the teeth 70 b, the second blade 12 b may be rotated into the desired rotational position.

In alternative embodiments, the blade adjustment mechanism may have a different structure. Referring to FIGS. 6-9B, for example, the blade adjustment mechanism of the exemplary surgical access device 100 may include a screw 102 received within an internally threaded bushing 104 positioned in a connection node 126 and connected to the proximal end 118 of a tissue engaging blade 112 of the surgical access device 100. Rotation of the screw 102 causes the bushing 104 to move along the axis of the screw 102 thereby adjusting the rotational position of a rotationally adjustable blade 112. In particular, referring to connection node 126 a of the exemplary surgical access device 100 and to FIGS. 9A-B, a screw 102 a is positioned through an opening in the top surface of the frame 114 and through the internally threaded bushing 104 a positioned in the connection node 126 a. The exemplary screw 102 a is cannulated at the distal end of the screw 102 a. A bolt 106 a positioned through an opening in the bottom surface 116 of the frame 114 is positioned within the cannulated distal end of the screw 102 a to inhibit movement of the screw 102 a off of a screw axis 108 a that is oriented approximately perpendicular to the plane defined by the bottom surface 116 of the frame 114. Rotation of the screw 102 a in a first direction causes the first blade 112 a to rotate about shaft 130 a from a first, closed position, illustrated in FIG. 6 and FIG. 9B, toward a second, fully expanded position, illustrated in FIGS. 7 and 9A. Rotation of the screw 102 a in a second direction, opposite the first direction, causes the first blade 112 a to rotate about shaft 130 a from an expanded position toward the closed position.

Referring to FIG. 10, an exemplary embodiment of a surgical access device 200 having an alternative blade adjustment mechanism is illustrated. FIG. 10 illustrates an exemplary connection node 226 of the surgical access device 200. The blade adjustment mechanism of the exemplary surgical access device 200 includes a screw 202 received within a threaded hole 203 provided in the frame 214. The screw 202 has a screw axis 208 that is oriented generally parallel to the plane defined by the bottom surface 216 of the frame 214. The distal end of the screw 202 may engage the proximal end 218 of the tissue engaging blade 212. Movement of the screw 202 along a screw axis 208 relative to the frame 214 adjusts the rotational orientation of the first blade by rotating the blade 212 about shaft 230.

Referring to FIG. 11, an exemplary embodiment of a surgical access device 300 having an alternative blade adjustment mechanism is illustrated. FIG. 11 illustrates an exemplary connection node 326 of the surgical access device 300. The blade adjustment mechanism of the exemplary surgical access device 300 includes cable 380 positioned through an opening 384 in the frame 314 of the surgical access device 300. The cable 380 may be connected at one end to a tissue engaging blade 312. At the other end, the cable 380 may be connected to a wheel 382 about which the cable 380 may be wound. Rotation of the wheel 382 can cause the cable 380 to pull on the blade 312 and rotate the blade 312 about the shaft 330. A spring may be provided to bias the blade 312 to the first, closed position.

Referring to FIG. 12, an exemplary embodiment of a surgical access device 400 having an alternative blade adjustment mechanism is illustrated. FIG. 12 illustrates an exemplary connection node 426 of the surgical access device 400. The blade adjustment mechanism of the exemplary surgical access device 400 includes a rotatable disk 407 rotatably connected to the connection node 426 and engageable with the proximal end 418 of the tissue engaging blade 412. In the exemplary embodiment, the proximal end 418 of the blade 412 includes an arcuate surface for engaging the disk 407. Rotation of the disk 407 relative to the frame 414 adjusts the rotational orientation of the blade 412 by rotating the blade 412 about shaft 430. In certain exemplary embodiments, the disk 407 may be a gear having teeth for engaging teeth provided on the arcuate surface of the proximal end 418 of the blade 412.

Referring to FIG. 13, an exemplary embodiment of a surgical access device 500 having an alternative blade adjustment mechanism is illustrated. FIG. 13 illustrates an exemplary connection node 526 of the surgical access device 500. The blade adjustment mechanism of the exemplary surgical access device 500 includes a cavity 511 provided in the frame 514 for receiving the proximal end 518 of a tissue engaging blade 512. In the exemplary embodiment, the cavity 511 has a size and shape complementary to the size and shape of the proximal end 518 of the blade 512 and selected to allow the blade 512 to rotate relative to the frame 514. In the exemplary embodiment, for example, the proximal end 518 of the blade 512 may be approximately spherical in shape and the cavity 511 may include a seat that is approximately spherical in shape for engaging the proximal end 518 of the blade 512. A screw 513 or the like may be provided to fix the proximal end 518 of the blade 512 into contact with the seat of the cavity 511 and thereby inhibit rotation of the blade 512.

One skilled in the art will appreciate that other blade adjustment mechanisms may be employed to adjust the rotational position of a rotationally adjustable blade.

One or more of the blades of the surgical access device may have an adjustable length, e.g. the blade may telescope to selectively adjust the length of the blade. Referring to the exemplary embodiment illustration in FIGS. 6-9, for example, one or more of the blades 112 may include a primary blade 140 connected to the frame 114 and an adjustable blade 142 that is operatively coupled to the primary blade and is adjustable relative to the primary blade 140 along the length of the primary blade 140. In the exemplary embodiment, blades 112 a-d are adjustable in length and include a respective primary blade 140 a-d and a respective adjustable blade 142 a-d. Exemplary tissue engaging blades having an adjustable length are disclosed in U.S. Patent Application Publication No. 2005-0137461 A1, which is incorporated herein by reference. The telescoping blades may include a mechanism for selectively adjusting the position of the adjustable blade 142 relative to the primary blade 140. For example, the primary blade 140 may include a plurality of teeth 144 extending along the longitudinal axis of the primary blade 140 and the adjustable blade 142 may include a flexible tab 146 for engaging the teeth 144 of the primary blade 140. The surgical access device may be inserted through an incision with the adjustable blades 142 in place, as in the case of the exemplary surgical access device 100 illustrated in FIGS. 6-9. Alternatively, the surgical access device may be inserted through an incision without the adjustable blades in place, as in the case of the exemplary surgical access device 10 illustrated in FIGS. 1-5. In such embodiments, the surgical access device 10 may be inserted with the primary blades 40 a-d and one or more adjustable blades may be added after insertion.

The components of the surgical access devices disclosed herein may be manufactured from any biocompatible material including metals, such as stainless steel or titanium, polymers, or composite materials. The components, such as the blades and the frame, may be constructed from the same or different materials.

An exemplary method of providing minimally invasive access to spinal anatomy employing a surgical access device disclosed herein may include making a skin incision for insertion of the surgical access device. The incision initially may be less than the diameter of the surgical access device in the closed configuration (e.g., with the blades of the device in the first, closed position). The incision may be expanded to accommodate the surgical access device by dilation, for example, by placing one or more dilators through the incision to expand the incision in a stepwise manner. The dilators may be employed to separate or dissect the underlying tissue to the target spinal anatomy. Alternatively, the surgeon may employ his finger or the surgical access device to dissect the underlying tissue and to expand the initial incision.

The blades of a surgical access device may be inserted through the incision and the distal ends of the blades may be advanced into proximity to the spinal anatomy. The blades are preferably advanced in the first, closed position, in which the blades are proximate to each other to form a continuously approximately enclosed access channel between the frame, which located at the surface of the skin, and the distal ends of the blades. One or more of the blades may be rotated, using a blade adjustment mechanism, independent of the other blade to selectively expand the access channel. In the case of the exemplary surgical access device 10 and the exemplary surgical access device 100, rotational adjustment of some or all of the blades of the device expands the access channel, particularly at the distal end of the access channel, thereby creating greater working space at proximate the target spinal anatomy. In addition, the length of the working channel may be increased by advancing an adjustable blade of one of the plurality of blades relative to a primary blade along a longitudinal axis of the primary blade.

Any number of surgical procedures may be performed through the access channel including, for example, removal of some or all of one or more discs, placement of bone fusion promoting material, placement of an spine arthroplasty device such as an artificial disc, placement of spinal implants such as hooks, rods, and screws.

After the surgical procedure is performed, the surgical access device may be returned to the closed configuration and removed from the incision.

While the devices and methods of the present invention have been particularly shown and described with reference to the exemplary embodiments thereof, those of ordinary skill in the art will understand that various changes may be made in the form and details herein without departing from the spirit and scope of the present invention. Those of ordinary skill in the art will recognize or be able to ascertain many equivalents to the exemplary embodiments described specifically herein by using no more than routine experimentation. Such equivalents are intended to be encompassed by the scope of the present invention and the appended claims. 

1. A surgical access device comprising: a proximal frame of fixed construction; and a plurality of tissue engaging blades connected to the frame, the plurality of tissue engaging blades including a first blade that is rotatable, independent of other blades, about an axis that is oriented approximately parallel to a plane defined by the proximal frame.
 2. The surgical access device of claim 1, wherein at least one of the plurality of tissue engaging blades comprises a primary blade connected to the proximal frame, and an adjustable blade operatively coupled to the primary blade and adjustable relative to the primary blade along a longitudinal axis of the primary blade.
 3. The surgical access device of claim 2, wherein the primary blade includes a plurality of teeth extending along the longitudinal axis of the primary blade and the adjustable blade includes a flexible tab for engaging the teeth of the primary blade.
 4. The surgical access device of claim 1, further comprising a blade adjustment mechanism for selectively adjusting the rotational position of the first blade.
 5. The surgical access device of claim 4, wherein the blade adjustment mechanism comprises a pawl pivotally connected to the frame for selectively engaging a plurality of teeth provided at a proximal end of the first blade.
 6. The surgical axis device of claim 5, wherein the pawl is biased by a spring into contact with the teeth.
 7. The surgical access device of claim 6, wherein the teeth are provide on an arcuate surface of the proximal end of the first blade.
 8. The surgical access device of claim 4, wherein the blade adjustment mechanism comprises a screw received within a threaded bushing connected to the first blade, rotation of the screw causing the bushing to move along an axis of the screw to adjust the rotational orientation of the first blade.
 9. The surgical access device of claim 8, wherein the screw axis is oriented approximately perpendicular to the plane defined by the frame.
 10. The surgical access device of claim 4, wherein the blade adjustment mechanism comprises a screw received within a threaded hole provided in the frame, the screw having a screw axis that is oriented approximately parallel to the plane defined by the frame, movement of the screw along a screw axis relative to the frame adjusts the rotational orientation of the first blade.
 11. The surgical access device of claim 4, wherein the blade adjustment mechanism comprises a cable connected to the first blade and positioned through the frame, wherein adjustment of the cable along the cable axis adjusts the rotational orientation of the first blade.
 12. The surgical access device of claim 1, wherein the first blade is directly rotationally connected to the frame.
 13. The surgical access device of claim 1, wherein the plurality of tissue engaging blades includes a second blade that is rotatable about an axis that is oriented approximately parallel to a plane defined by the proximal frame, the second blade being positioned opposite the first blade.
 14. The surgical access device of claim 13, wherein the plurality of tissue engaging blades includes a third blade that is rotatable about an axis that is oriented approximately parallel to a plane defined by the proximal frame, the third blade being positioned between the first blade and the second blade.
 15. A surgical access device comprising: a proximal frame of fixed construction, the proximal frame have an approximately planar bottom surface; a first blade connected to the proximal frame and rotatable about a first axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame; a second blade connected to the proximal frame and rotatable about a second axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame, the second blade positioned opposite the first blade; a third blade connected to the proximal frame and rotatable about a third axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame; the third blade being positioned between the first blade and the second blade; and a fourth blade connected to the proximal frame and rotatable about a fourth axis that is oriented approximately parallel to a plane defined by the bottom surface of the proximal frame, the fourth blade being positioned opposite the third blade.
 16. The surgical access device of claim 15, wherein first, second, third, and fourth blades each comprise a primary blade connected to the proximal frame, and an adjustable blade operatively coupled to the primary blade and adjustable relative to the primary blade along a longitudinal axis of the primary blade.
 17. The surgical access device of claim 16, further comprising: a first blade adjustment mechanism for selectively adjusting the rotational position of the first blade, a second blade adjustment mechanism for selectively adjusting the rotational position of the second blade, a third blade adjustment mechanism for selectively adjusting the rotational position of the third blade, and a fourth blade adjustment mechanism for selectively adjusting the rotational position of the first blade.
 18. The surgical access device of claim 16, wherein the first axis, the second axis, the third axis, and the fourth axis are positioned in a common plane.
 19. The surgical access device of claim 16, wherein the first blade, the second blade, the third blade, and the fourth blade are rotationally adjustable independent of one another.
 20. A method of providing minimally invasive access to spinal anatomy, the method comprising: making an incision, inserting a plurality of blades of a surgical access device through the incision, the surgical access device comprising a proximal frame and the plurality of blades connected to the proximal frame, advancing the distal ends of the plurality blades into proximity to the spinal anatomy, and rotating a first one of the blades independent of the other blades about a rotation axis that is oriented approximately parallel to an axis defined by the proximal frame to expand the access channel.
 21. The method of claim 20, further comprising increasing the length of the working channel by advancing an adjustable blade of one of the plurality of blades relative to a primary blade along a longitudinal axis of the primary blade.
 22. The method of claim 20, further comprising rotating a second one of the blades independent of the other blades about a rotation axis that is oriented approximately parallel to an axis defined by the proximal frame to expand the access channel.
 23. The method of claim 22, further comprising rotating a third one of the blades independent of the other blades about a rotation axis that is oriented approximately parallel to an axis defined by the proximal frame to expand the access channel.
 24. The method of claim 23, further comprising rotating a fourth one of the blades independent of the other blades about a rotation axis that is oriented approximately parallel to an axis defined by the proximal frame to expand the access channel.
 25. The method of claim 20, wherein the distal ends of the blades of the surgical access device are advanced through a posterior approach into proximity to posterior spinal anatomy.
 26. The method of claim 20, wherein the distal ends of the blades of the surgical access device are advanced through an anterior approach into proximity to anterior spinal anatomy.
 27. The method of claim 20, further comprising performing a surgical procedure on the spinal anatomy through the access channel.
 28. The method of claim 27, further comprising rotating the first blade into contact with other blades, after performing the surgical procedure, to return the surgical access device to the closed configuration and removing the surgical access device from the incision.
 29. The method of claim 20, further comprising expanding the incision and inserting the plurality of blades of a surgical access device through the expanded incision.
 30. The method of claim 20, wherein the distal ends of the plurality of blades are advanced into proximity to the spinal anatomy with the blades in a closed configuration in which the blades contact each other to form a continuous enclosed access channel between the frame and the distal ends of the blades.
 31. The surgical access device of claim 4, wherein the blade adjustment mechanism comprises a gear rotationally connected to the frame, wherein rotation of the gear adjusts the rotational orientation of the first blade.
 32. The surgical access device of claim 4, wherein the blade adjustment mechanism comprises a cavity provided in the frame having an approximately spherical seat for receiving a proximal end of the first blade and a screw for selectively engaging the proximal end of the first blade and positioning the proximal end of the blade into contact with the seat. 